Answer:
The percent probability of winning a prize=40%.
and not winning prize=60%.
We are asked to find the probability that Hannah only has to buy 3 or less boxes before getting a prize.
Let the random used is x=0,1,2,3 ( where
- 0 denotes that we got the success in first attempt.
- 1 denotes that first bag does not contain prize but we get success in second attempt.
- 2 denotes that we did not get success in 2 attempts but in third we get the success.
- 3 denotes that the success is not obtained in any of the three attempts )
Hence, the probability that the first box will contain prize=
![(40)/(100)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/4xie4j8576c9bjf6ik4pd5dohmnu2cie22.png)
The probability that the first box will not contain prize but second will=
![(60)/(100)*(40)/(100)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/zqvf87emfoedzxfym6422tjowtoemq3ygv.png)
The probability that the first and second box will not contain prize but third will=
![(60)/(100)*(60)/(100)*(40)/(100)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/4ds6dcsxbnu5cv1t243sljd5o7l75xpmf4.png)
The probability that the first and second box will not contain prize but third will=
![(60)/(100)*(60)/(100)*(40)/(100)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/4ds6dcsxbnu5cv1t243sljd5o7l75xpmf4.png)
The probability that the prize is not contained in first, second and third box=
![(60)/(100)+*(60)/(100)*(60)/(100)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/oauiwpapk3nc1hpuzseqxxewybrsei72e7.png)
Hence, the total probability=
![(40)/(100)+(60)/(100)*(40)/(100)+(60)/(100)*(60)/(100)*(40)/(100)+(60)/(100)+*(60)/(100)*(60)/(100)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/jpgmhyo91o0lxsd31yf1nupa896g20nmjb.png)